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Equity Compensation and Employee Benefit Plans (Narrative) (Details) | 12 Months Ended
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Dec. 31, 2018 USD ($) shares | Dec. 31, 2017 USD ($) shares | Dec. 31, 2016 USD ($) shares
Equity Compensation [Abstract] |  |  |
Maximum shares of common stock | shares | 20,000,000 |  |
Maximum annual shares awarded to employee | shares | 500,000 |  |
Shares available for granting additional awards | shares | 7,077,807 |  |
Unrecognized compensation cost of non-vested equity compensation awards | $ | $ 10,400,000 |  |
Unrecognized compensation cost of non-vested equity compensation awards expected to be recognized over a weighted average period (years) | 2 years |  |
Maximum annual stock purchase plan contributions by plan participants | $ | $ 20,000 |  |
Percentage of company matching contribution to employee stock purchase plan | 15.00% |  |
Percentage of interest accrues on purchase plan contributions | 5.25% |  |
Number of participants in executive nonqualified excess plan | 42 |  |
Number of options granted | shares | 0 | 0 | 0
Stock Options |  |  |
Equity Compensation [Abstract] |  |  |
Maximum period for exercisable options (years and days) | 10 years 1 day |  |
Stock Options | Minimum |  |  |
Equity Compensation [Abstract] |  |  |
Vesting period (months) | 24 months |  |
Stock Options | Maximum |  |  |
Equity Compensation [Abstract] |  |  |
Vesting period (months) | 72 months |  |
Restricted Stock |  |  |
Equity Compensation [Abstract] |  |  |
Fair value of awards vested | $ | $ 3,100,000 | $ 4,400,000 | $ 4,300,000
Restricted Stock | Minimum |  |  |
Equity Compensation [Abstract] |  |  |
Vesting period (months) | 12 months |  |
Restricted Stock | Maximum |  |  |
Equity Compensation [Abstract] |  |  |
Vesting period (months) | 60 months |  |
Performance Shares |  |  |
Equity Compensation [Abstract] |  |  |
Fair value of awards vested | $ | $ 1,300,000 | $ 1,000,000 | $ 1,600,000
Performance Shares | Minimum |  |  |
Equity Compensation [Abstract] |  |  |
Vesting period (months) | 12 months |  |
Performance Shares | Maximum |  |  |
Equity Compensation [Abstract] |  |  |
Vesting period (months) | 60 months |  |

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- Definition Unrecognized cost of unvested share-based compensation awards. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Net number of share options (or share units) granted during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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